Processing and Characterization of Hybrid Composite Materials Made of Recycled HDPE and Mechanically Recycled Glass Fiber Thermoset Composites

Abstract

Household plastic waste and industrial polymer matrix composite material scrap present two scales of problems that can lead to pollution and other environmental issues. Recycling waste and scrap has become increasingly important and has drawn tremendous attention as a promising approach to solving the growing polymer pollution issue. This study aims to create energy-efficient and scalable procedures to manufacture hybrid composite materials using household thermoplastic waste and industrial thermoset matrix composite scrap for the first time to our best knowledge, and evaluate the structural performance of upcycled fiber-reinforced composites. Recycled scrap of pultruded glass fiber vinyl ester composite (rComposite) was mechanically split with an energy-efficient process and subsequently molded with recycled household high-density polyethylene (rHDPE) waste to produce thermoset composite reinforced thermoplastic matrix (rComposite/rHDPE) composites at different rComposite contents, i.e., 20, 27, and 35 wt%. Various characterization methods, including Fourier transform infrared spectroscopy, differential scanning calorimetry, optical microscopy, and scanning electron microscopy analyses, were performed to evaluate the constituent materials and the molded composite. Mechanical testing was also conducted to evaluate the mechanical properties of the composites with different rComposite contents. It was found that the tensile and flexural properties of the rComposite/rHDPE composite increased with increasing rComposite content. There was a 256% increase in tensile strength and an 885% increase in tensile modulus for the 35%-rComposite reinforced rHDPE composite over neat rHDPE, respectively. Overall, this study presents a potential approach of recycling household plastic waste and polymer matrix composite material scrap by developing a hybrid composite material with great mechanical properties.

Keywords

Composite material / Recycling / Plastic bag / Pultrude composite / Glass fiber composite

References

[1] Ning H. Thermoplastic Composites: Principles and Applications; Walter de Gruyter GmbH & Co KG: Berlin, Germany, 2021.

[2] Davim JP. Biomedical Composites: Materials, Manufacturing and Engineering; Walter de Gruyter: Berlin, Germany, 2013.

[3] Davim JP . Composite materials: A bibliometric analysis. AIMS Mater. Sci. 2024, 11, 1145-1148. DOI: 10.3934/matersci.2024055

[4] Available online: https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/frequent-questions-regarding-epas-facts-and#:~:text=Data%20web% (accessed on 10 July 2025).

[5] Parikh HH, Gohil PP . Tribology of fiber reinforced polymer matrix composites-A review. J. Reinf. Plast. Compos. 2015, 34, 1340-1346. DOI: 10.1177/0731684415591199

[6] Gourmelon G. Global Plastic Production Rises, Recycling Lags2015. Available online: https://www.igpn.org/news/2015/01/global_plastic_production_rise.html (accessed on 10 July 2025).

[7] The Compelling Facts About Plastics. 2008. Available online: https://plasticseurope.org/wp-content/uploads/2021/10/2006-Compelling-facts.pdf (accessed on 10 July 2025).

[8] Geyer R, Jambeck JR, Law KL . Production, use, and fate of all plastics ever made. Sci. Adv. 2017, 3, e1700782. DOI: 10.1126/sciadv.1700782

[9] Bream CE, Hornsby PR . Comminuted thermoset recyclate as a reinforcing filler for thermoplastics: Part I characterisation of recyclate feedstocks. J. Mater. Sci. 2001, 36, 2965-2975. DOI: 10.1023/A:1017962722495

[10] Patel SH, Xanthos M . Environmental issues in polymer processing: A review on volatile emissions and material/energy recovery options. Adv. Polym. Technol. 2001, 20, 22-41. DOI: 10.1002/1098-2329(200121)20:1<22::AID-ADV1002>3.3.CO;2-F

[11] Dahlbo H, Poliakova V, Mylläri V, Sahimaa O, Anderson R. Recycling potential of post-consumer plastic packaging waste in Finland. Waste Manag. 2018, 71, 52-61. DOI: 10.1016/j.wasman.2017.10.033

[12] Murat BIS, Kamalruzaman MS, Azman MHN, Misroh MF . (Eds). Assessment of mechanical properties of recycled HDPE and LDPE plastic wastes. IOP Conf. Ser. Mater. Sci. Eng. 2020, 957, 012046. DOI: 10.1088/1757-899X/957/1/012046

[13] Chen RS, Chai YH, Olugu EU, Salleh MN, Ahmad S . Evaluation of mechanical performance and water absorption properties of modified sugarcane bagasse high-density polyethylene plastic bag green composites. Polym. Polym. Compos. 2021, 29, S1134-S1143. DOI: 10.1177/09673911211049058

[14] Maheshwari A, Azarfam MY, Chaudhari S, Switzer C, Hanan JC, Bandla S, et al. Composites from Post-Consumer Polypropylene Carpet and HDPE Retail Bags. In Technology Innovation for the Circular Economy: Recycling, Remanufacturing, Design, Systems Analysis and Logistics; 2024; pp. 333-342. Available online: https://onlinelibrary.wiley.com/doi/10.1002/9781394214297.ch26 (accessed on 25 July 2025).

[15] Al-Talib AA, Abdullah NF, Hamid ARA, Kit WW, Hoe TJ. Investigation of the Mechanical Properties and Applicability of HDPE Recycled Plastic Bags. Available online: https://alife-robotics.co.jp/members2023/icarob/data/html/data/OS/OS27/OS27-5.pdf (accessed on 25 July 2025).

[16] Abdel Tawab O, Amin M, Ibrahim M, Abdel Wahab M, Abd El Rahman E, Hassanien R, et al. Recycling waste plastic bags as a replacement for cement in production of building bricks and concrete blocks. J. Waste Resour. Recycl. 2020, 1, 202. Available online: https://www.researchgate.net/publication/339613441_Recycling_Waste_Plastic_Bags_as_a_Replacement_for_Cement_in_Production_of_Building_Bricks_and_Concrete_Blocks (accessed on 25 July 2025).

[17] Vedernikov A, Safonov A, Tucci F, Carlone P, Akhatov I . Pultruded materials and structures: A review. J. Compos. Mater. 2020, 54, 4081-4117. DOI: 10.1177/0021998320922894

[18] Correia JR. Pultrusion of advanced composites. In Advanced Fiber-Reinforced Polymer (FRP) Composites for Structural Applications; Elsevier: Amsterdam, The Netherlands, 2023; pp. 137-177.

[19] Feng P, Wang J, Wang Y, Loughery D, Niu D . Effects of corrosive environments on properties of pultruded GFRP plates. Compos. Part B: Eng. 2014, 67, 427-433. DOI: 10.1016/j.compositesb.2014.08.021

[20] Yang S, Liu W, Fang Y, Huo R . Influence of hygrothermal aging on the durability and interfacial performance of pultruded glass fiber-reinforced polymer composites. J. Mater. Sci. 2019, 54, 2102-2121. DOI: 10.1007/s10853-018-2944-6

[21] Kasim H, Shih Y-C, Ning H, Pillay S. Upcycling epoxy-glass thermoset waste into high-performance polyethylene composites. Compos. Struct. 2026, 377, 119880. DOI: 10.1016/j.compstruct.2025.119880

[22] Andrew JJ, Srinivasan SM, Arockiarajan A, Dhakal HN. Parameters influencing the impact response of fiber-reinforced polymer matrix composite materials: A critical review. Compos. Struct. 2019, 224, 111007. DOI: 10.1016/j.compstruct.2019.111007

[23] Castro ACM, Carvalho JP, Ribeiro MC, Meixedo JP, Silva FJ, Fiúza A, et al. An integrated recycling approach for GFRP pultrusion wastes: Recycling and reuse assessment into new composite materials using Fuzzy Boolean Nets. J. Clean. Prod. 2014, 66, 420-430. DOI: 10.1016/j.jclepro.2013.10.030

[24] Kandasamy V, Subramanian A, Subramanian S, Rajendran S. Mechano-chemical upcycling of pultruded composite waste for reuse in concrete mixture. Matéria 2024, 29, e20240348. DOI: 10.1590/1517-7076-rmat-2024-0348

[25] Kasim H, Mohamed M, Ning H, Pillay S. Recycling of Pultruded Vinyl Ester Thermoset Scraps into Polyethylene Composites: Toward Circular Composite Manufacturing. J. Compos. Sci. 2025, 9, 641. DOI: 10.3390/jcs9120641

[26] Frej HBH, Léger R, Perrin D, Ienny P, Gérard P, Devaux J-F . Recovery and reuse of carbon fibre and acrylic resin from thermoplastic composites used in marine application. Resour. Conserv. Recycl. 2021, 173, 105705. DOI: 10.1016/j.resconrec.2021.105705

[27] Ribeiro MCS, Fiúza A, Castro AC, Silva F, Meixedo JP, Dinis ML, et al. Recycling of Pultrusion Production Waste into Innovative Concrete-Polymer Composite Solutions. Adv. Mater. Res. 2011, 295, 561-565. DOI: 10.4028/www.scientific.net/AMR.295-297.561

[28] Krauklis AE, Karl CW, Gagani AI, Jørgensen JK . Composite material recycling technology-state-of-the-art and sustainable development for the 2020s. J. Compos. Sci. 2021, 5, 28. DOI: 10.3390/jcs5010028

[29] Scaffaro R, Di Bartolo A, Dintcheva NT . Matrix and filler recycling of carbon and glass fiber-reinforced polymer composites: A review. Polymers 2021, 13, 3817. DOI: 10.3390/polym13213817

[30] Butenegro JA, Bahrami M, Abenojar J, Martínez MÁ. Recent progress in carbon fiber reinforced polymers recycling: A review of recycling methods and reuse of carbon fibers. Materials 2021, 14, 6401. DOI: 10.3390/ma14216401

[31] Angulo C, Brahma S, Espinosa-Dzib A, Peters R, Stewart KME, Pillay S, et al. Development of hemp fiber composites with recycled high density polyethylene grocery bags. Environ. Prog. Sustain. Energy 2021, 40, e13617. DOI: 10.1002/ep.13617

[32] Chawla KK. Composite Materials: Science and Engineering; Springer Science & Business Media: Berlin/Heidelberg, Germany, 2012.

[33] Li S, Wang X, Xue B, Feng D, Liu Y, Jiang W . Flower-like Ag/Ag₂O/Bi₁₂O₁₇Cl₂ heterojunction for photocatalytic removal of antibiotics: Synergetic effect of plasmonic effect and p-n heterojunction. J. Mater. Sci. Technol. 2026, 246, 237-246. DOI: 10.1016/j.jmst.2024.12.088

[34] Borjan D, Knez Z, Knez M . Recycling of Carbon Fiber-Reinforced Composites-Difficulties and Future Perspectives. Materials 2021, 14, 4191. DOI: 10.3390/ma14154191

[35] Ning H, Lu N, Hassen AA, Chawla K, Selim M, Pillay S. A review of Long fibre thermoplastic (LFT) composites. Int. Mater. Rev. 2020, 65, 164-188. DOI: 10.1080/09506608.2019.1585004